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Ocular Motility > Fixations and Visual Attention > Flashcards

Fixations and Visual Attention Flashcards

1
Q

T/F The eye is NEVER motionless

A

true

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2
Q

What is the functional fovea area?

A

+/- 30’ of arc discrete area on the retina within which images are held

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3
Q

What happens to the discrete area on the retina the longer fixation is held?

A

longer fixation=larger area

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4
Q

What are three types of movements (subconscious)

A

tremors, drifts, and micro saccades

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5
Q

What is a tremor?

A

constant, high frequency 30-100 Hz, amp 20” of arc, no VA change

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6
Q

What is a drift?

A

low velocity <0.5 Hz, crosses 15 cones/sec, irregular movement

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7
Q

What is a microsaccade?

A

1-2/sec, corrects drift, large dynamic overshoot component, error correcting, amp of 5’ of arc, amplitude dependent relation

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8
Q

Which movement is always binocular?

A

micro saccades

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9
Q

Which movement do eyes perform most of the time?

A

drifts (95%)

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10
Q

Which movement is superimposed over the other two?

A

tremors

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11
Q

What factors impact movements?

A

peripheral gaze direction increases probability of movement, darkness: less steady and more drifts/correcting saccades

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12
Q

During normal fixations, what is the relationship between drift and microsaccades?

A

Drifts and micro saccades move in the opposite direction and drift is error producing and occurs 95% of the time while micro saccades are error correcting

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13
Q

What two things make drifts worse?

A

greater gaze angle and darkness– evidence of leaky neural integrator

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14
Q

What improves accuracy of fixations?

A

visual feedback

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15
Q

Even w/o visual feedback, deviation is typically only a few degrees, what does this suggest?

A

use of EOM proprioception and tactile info from lids

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16
Q

What are the three main types of abnormal fixation movements?

A

slow drift, saccadic intrusion, and nystagmus

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17
Q

What is a slow drift?

A

found with functional amblyopia, amp 1 degree, velocity <3 deg/sec, irregular, slow frequency <0.5 Hz

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18
Q

T/F VT will NOT fix a slow drift

A

false

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19
Q

What is a saccadic intrusion

A

large fixational saccade that interrupt attempts at fixation; three kinds= square wave jerks, macro square wave jerks, and macro saccadic oscillations

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20
Q

What is an aberrant tremor?

A

seen w/ EEG or coma patient because other movements usually cover them; baseline state of brainstem

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21
Q

What is a square wave jerk?

A

away from the target and then back 200 msec later; dx cerebellar disease if freq/amp increases

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22
Q

What is a macro square wave jerk?

A

larger, more frequency duration off target 100 msec; dx cerebellar disease and multiple sclerosis

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23
Q

What is a macro saccadic oscillation?

A

saccadic sequence increasing then decreasing amplitude to either side of a target; ALSO dx cerebellar disease

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24
Q

Which of the abnormal fixation movements might you see in clinic?

A

macro square wave jerks

25
T/F fixation in amblyopia improves with feedback
true
26
Explain the feedback received by amblyopic patients in the study
goggles w/ a computer program track fixation, and when the eye leaves the target, the computer makes an auditory stimulus until focus is corrected-- allowing the patient to learn to control fixation
27
What happens during a fixation?
EOMs keep the eyes still with respect to the visual environment as the head/body moves
28
What two systems promote visual stabilization?
VOR vestibulo-ocular and OKN optokinetic
29
What prevents image degradation?
micro saccades and the troxler effect
30
What is true of the scan path of a photograph under free exploration?
most of the focus is on the face and other objects
31
What was the Yarbus free exploration study?
subjects typically focus on faces and objects; under command to judge material status look at clothes and servants; under command to judge age differences look at faces and height
32
What is true of an expert viewer as compared to a novice?
Expert has fewer fixations, shorter duration, less random search pattern of fixations-- uses vision to derive meaning
33
What is the primary purpose of the visual system?
to derive meaning and the direction of action
34
What is a "consequence" of visual attention?
selection of an area to pay attention to will cause the omission of some other things (figure vs ground) due to limited scope of attention
35
What happens to things we focus on during visual attention?
they get amplified in the system, allowing for persistence of their image for further inspection by higher order process
36
Most visual problems are problems of ____ not _____
omission not commission
37
What are the components of the visual attention system?
attention window and visual buffer, encoding processes, memory, information look up, and attention shifting
38
What is inside the attention window?
figure
39
What is in the visual buffer?
ground
40
____ emerges from ____
figure, ground
41
What is the figure processed by?
object properties--what
42
What is the ground processed by?
spatial properties-- where
43
What does associative memory do?
accesses previous info and gives context
44
What happens with attention shifting?
restart the process, does not require an eye movement
45
What steps does attention/shape shifting entail?
disengage, move, engage
46
T/F we have to have a stimulus to shift attention
false, we have volitional control, we can also inhibit a shift of attention to a stimulus
47
Which steps of shape shift change the size of the attention window?
disengage and move
48
What step do patients with autism have trouble with?
engage
49
What step do patients with parkinsons have trouble with?
disengage
50
What step do myopes have trouble with?
disengage
51
What step do ADHD patients have trouble with?
inhibition
52
What is sensory memory?
the what system
53
What is motor memory?
the where system
54
Object recognition in human vision is provided by:
separate but simultaneous processing and representation of what and where information at high levels of the visual system
55
Frame of reference is attached to...
the basic feature at each fixation point and includes what and where data
56
Mechanisms of visual attention use ____ info to direct sequential image processing (what to do next)
where-- context and planning
57
Mechanisms provide comparisons of ___ and ___ object features in each fixation
current and expected
58
How do we look at a face?
One eye to the other then down the nose and around the face

Ocular Motility (13 decks)

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